This invention relates to an apparatus for applying a constant centering force on the edges of tire tread rubber as it travels across an application conveyor to a tire drum. Conicity offset adjustment is also provided by adjusting the position of the center line of the tread relative to the center line of the tire building drum.
Apparatus for applying a uniform force perpendicular to the axis of the tread as it travels across an application conveyor toward a tire building drum is shown and described in U.S. Pat. No. 5,389,187. The method of applying the force is shown and described in U.S. Pat. No. 5,534,093. In accordance with the method and apparatus of these patents, the tread is conveyed on a conveyor between two self-centering guides which are slidably mounted on a frame positioned over the conveyor. The guides have parallel rows or rollers for engaging opposite edges of the tread and are urged toward the tread edges by a pneumatic, double-acting piston cylinder assembly connected to the guides by pulleys and cables. The piston cylinder assembly is connected to a centering screw for adjusting the position of the tread centerline.
U.S. Pat. No. 3,413,174 is directed to a conveyor apparatus having guide rolls for adjusting the longitudinal center line of the tread, however, no provision is made for accommodating a variable width of the tread. U.S. Pat. No. 4,261,286 is directed to a conveyor apparatus having a pair of threaded shafts to rotate in threaded shoulder guides urging them towards the center of a tread with a motor rotating the shafts, however, there is no disclosure of a single ball screw extending between supporting frame members for moving two tire tread guides together and providing a continuous constant force against each side of a tire tread.
The publication Grundlagen der Preumatik Auto Krausskopf-Verlag GmbH, Mainz sets forth the rotational momentum behavior of compressed air motors. With reference made to FIG. 40 which shows characteristic curves of a compressed air motors has a function of xe2x80x9cnxe2x80x9d (rotation speed) there is no disclosure of using a pneumatic rotary actuator which does not rotate at a rotational speed, but only applies torque to a ball screw for urging nut members of guides toward the edges of a tread.
The present invention is directed to apparatus for applying a constant centering force on the edges of tread rubber as it is carried by an application conveyor toward a tire building drum. The constant centering force is provided by a ball screw and nut assembly, with the ball screw torque controlled by a pneumatic rotary actuator connected to the screw. An adjustment sleeve provides conicity offset adjustment by moving the entire ball screw and nut assembly laterally along the axis of the ball screw whereby the position of the center line of the tread may be adjusted slightly relative to the center line of the tire building drum.
In accordance with one aspect of the invention, there is provided apparatus for conveying a tire tread comprising a conveyor with two guides extending over the conveyor and having rollers engageable with side edges of the tread, characterized by the guides having nut members engageable with a ball screw extending between supporting frame members for moving the guides together or apart by rotating the ball screw and torque applying means including a pneumatic rotary actuator connected to the ball screw for applying torque to the ball screw to urge a nut member of a first one of the guides toward a first edge of the tread and a nut member of a second one of the guides toward a second edge of the tread and the torque applying means including a pneumatic rotary actuator connected to the ball screw providing a continuous constant force at each side of the tire tread by the rollers while in contact with the tread regardless of the variation in width of the tread, a clutch mounted between the ball screw and the pneumatic rotary actuator at a first end of the hall screw and manual means to rotate the screw mounted at a second end of the screw whereby the initial spacing of the guides may be provided by manually rotating the ball screw and whereby the torque forces may be applied by actuating the clutch to engage the pneumatic rotary actuator. Further embodiments of the invention are defined in the dependent claims.